Production of carbon tetrachloride



June 23, 1942. J. E. BEANBLossoM PRODUCTION OF CARBON TETRACHLORIDE Filed Nov. 20, 1940 Patented June 23, 1942 PRODUCTION F CARBON TETRACHLORIDE Joy E. Beanblossom, Niagara Falls, N. Y., assignor to Hooker Electrochemical Company,

Niagara Falls, N. Y., a corporation of New York Application November 20, 1940, Serial No. 366,427

(Cl. 26o-664) Claims.

My process may be exemplified by the chlorination of carbondisulphide to produce carbon tetrachloride.

The fundamental reaction of carbon disulphide with chlorine is as follows:

This reaction readily goes to substantial completion, but there is not always a suiiicient demand for the S2C12 to render the process based on this reaction commerciallypracticable. It is therefore necessary to nd a way to return the sulphur monochloride to the process; also to remove from the system at some stage a quantity of sulphur equivalent to that introduced as CS2. Herein lies one of the chief difficulties in the way of production of carbon tetrachloride from carbon disulphide.

Sulphur monochloride may be considered a chlorinating agent and as such it may be reacted with more carbon disulphide. However, in an ordinary batch operation this reaction will not go to completion. The incomplete reaction may,

for purposes of illustration, be written as follows:

Moreover, if an attempt be made to distill 01T the product it is found that thereaction tends to reverse and th product comes oi mixed with CS2, from which its separation is diilicult.

Reaction 2 can, if preferred, be carried out so as to leave no unreacted S2Cl2, by using an excess of CS2, as follows:

However, the diiculty of separating the product from the sulphur and CS2 still remains.

Instead of the elemental chlorine of Equation l sulphur dichloride may be used as the chlorinating agent. The reaction is then as follows:

CS2+2SCl2 0.1CS2+0.2S2Cl2+0.9CC14+3.4S (5) As in the case of Reaction 2, if an attempt be made to distill off the product the reaction tends to reverse and the product comes off contaminated with CS2.

Various expedients have been tried in order to induce Reactions 2 and 5 to go to completion, such as carrying out the reaction under pressure and in the presence of catalysts. However, these efforts have been only partially successful. Moreover, even if these reactions went to completion the difficulty. of distilling off the product from the sulphur would still remain, as the CCl4 tends to react with the sulphur, to form CS2 and S2Cl2.

A more successful way of overcoming the diniculty is to alternate Reactions 1 and 3, distilling off product after the first reaction, transferring the by product to the second reaction, removing the sulphur after the second reaction and recycling the residuals to the first reaction. This is of course quite a complicated matter, both as to the apparatus and as to the supervision required.

I have discovered that if Agaseous chlorine be introduced at an intermediate point in a plate column and carbon disulphide, which boils at 46.2 C., be introduced near the bottom of the column and caused to rise in the column in vapor phase and contact the chlorine, carbon tetrachloride may be drawn oli' at the top and sulphur at the bottom of the column. If the column is tall enough, the product will be of high purity, requiring very little subsequent treatment. The explanation of this is as follows:

At the point of introduction of the chlorine we have Reaction l taking place. The S2Cl2 of this reaction, boiling at 138 C. and being therefore liquid, descends from plate to plate, coming into contact with CS2 vapor, which bubbles through the liquid S2Cl2 on the plates. As the SzClz descends, more and more of it becomes decomposed, liberating elemental sulphur. At rst the sulphur is in solution in the S2012; As the S2Cl2 decreases and the sulphur increases a point is reached at which the latter exceeds the limit of its solubility in the former. Thereafter sulphur is present in molten form. On the lowermost plate, the molten sulphur is scrubbed with CS2. The residual S2Cl2 is thereby largely reacted out, as follows:

elimination of S2Cl2. Inpractice, this result is of course unattainable. The sulphur leaving the lowermost plate therefore contains a small quantity of S2012 which is easily recovered by distillation and may be recycled. Nevertheless, in a column of perfectly practicable height, by using a slight excess of chlorine I am able to produce CClq free from CSz. This is il. matter of the greatest importance, as it is impracticable, on a commercial scale, to separate CCl4 from CS2 by fractionation. Under the same conditions may product may contain tracesl of SClz and SzClz, but only in such amounts as can be removed without great difficulty or expense by fractionation or treatment with lime or both. The lime converts SCI: and SaClz to calcium sulphlte and calcium chloride, from which the product is sepa rated by another fractionation. The loss of yield in this purification step is negligible.

The net result of Reaction 6, following Reaction 1, as in my process, is therefore for practical purposes as follows:

If the CCl4 and 2S of Equation 'I were present together, the latter would be in solution in the former, and any attempt to separate them would result in a reversal of the reaction, producing CS: and SrClz. However, it will be noted that the CC14 is at the top and the 2S at the bottom of the column; hence the separation has already been made. It will also be noted that the 2S of Reaction 'l balances the sulphur introduced as CS2 and may be recycled as such.

Reaction 7, which in a batch operation would be entirely impossible is` therefore by my process rendered not only possible but practicable.

Instead of elemental chlorine, I may use sulphur dlchloride as the chlorinating agent, introducing it near the middle of the column as in the face ofthe chlorine. In that case we have Reaction 4 taking place at the point of its introduction. The sulphur dlchloride, which boils at 59 C., is preferably introduced in liquid phase. The SzCh produced by the reaction and the residual liquid SClz, if any, then descend from plate to plate against a rising stream of CS: vapor, which bubbles through the liquid on the plates. The SClz, if any, being the more reactive, soon disap pears, leaving only SzCh. As the SzCh continues to descend, the proportion of SzClz diminishes and the proportion of sulphur increases. Upon 'the lowermost plate, as in the previous case, we therefore have CS: scrubbing residual SaClz out of molten sulphur, in accordance with Reaction 6.

In a column of infinite height the net result of Reaction 6, following Reaction 4, as in my process, would for practical purposes beas follows:

In practice, when using a column of moderate height, I ilnd it desirable to supply an excess of SClz, which may be a-s much as 100 per cent over that of Reaction 4. Under these conditions, I am able to produce CC14 free from CS2 and containing only traces of SCh and SzClr, which are easily removed as previously noted and may be recycled. Assuming a 100 per cent excess of SClz, the net result of the reactions as they take place in my process is for practical purposes as follows:

Comparing Reaction 9 with Reaction 8 it will be seen that when an excess of SCI: is used the quantity of sulphur thrown out is diminished. However, if the excess is not more than 100 per cent the sulphur thrown out is suillcient to baiance that introduced as CS2 and may be recycled as such. It will also be seen thatthe excess SCi: appears as SzClz. This excess SzClz of course finds its way to the bottom plate along with the sulphur liberated by the reaction. -The latter therefore cornes oil.' in solution in the former, from which it may be readily, separated by distillation. The SzClz may then be chlorinated back to SCI: and recycled. The use of an excess of SCI: offers the advatnage that it enables the process to be operated at a temperature below C., the melting point of sulphur.

Reaction 9. which in a batch operation would be utterly impossible, is therefore by my process rendered entirely practicable.

Instead of sulphur dlchloride, I may employ sulphur monochloride as the chlorinating agent. In this case. there is no intermediate product and only one reaction takes place. However, unlike elemental chlorine and SClz, a slight excess of which causes the reaction to go to completion with respect to the CS2, SzClz does not react to completion with respect to CS2 unless in infinite excess. This condition is theoretically possible only in a column of inilnite height. In practice, therefore, I nd that SzClz by itself is a less satisfactory chlorinating agent than SClz.

When elemental chlorine is the chlorinating agent employed in my process the attack'on the iron of the column is very severe and the same 1s true to only a slightly less extent when sulphur dlchloride is the agent. I have therefore worked ou't a compromise in which I employ a mixture of sulphur dlchloride and sulphur monochloride which may be in the proportions of one molecule of the former to one and one-half of the latter. In this way I am able, without serious attack upon the reactor,v to secure a crude product free from CS: and containing only such minor quantiues or sci. and sich as can be readily euml; nated. 'I'he ilnal result of the reaction may then be summed up as follows:

the SzClr, is chlorinated to reconstitute the origl inal mixture oi.' sulphur monochloride andl -1 chloride, which is then recycled. di

Referring' to the drawing:

In this ligure Ihave illustrated, diagrammatically, typical apparatus for car in ou m ess when sulphur dlchloride op; rgixtre still!) 1stlilphur dlchloride and sulphur monochloride is used as the chlorinating reagent. In this drawing I indicates the storage for CS: and 2 the storage for SCi: or SCI: and SzClz. Storage I is replenished through pipe 3 and valve l. 'I'he CS: in storage I is lifted by pump l, driven by motor I and delivered through pipe 'I to bubble cap col: unm 8 at point 9. SClz or a mixture oi' SCI: and SzClz is raised by pump I 0 driven by motorl II and delivered through pipe I2 .and valve I3 to reactor 8 at point I4. Reactor l is provided with buibble'cap plates Il, ce ver Receiver ll'is refe pped stieg jacket I1. p muy equi with p descend from plate to late, fo

on the plates. The CS2, valxiorized rllllxlrnligetm the steam jacket, or by the heat oi? the reaction itself.' rises inthe column, bubblin of liquid on the plates. Y g through pools Il and, at its base, with re- The SClzand Sach in liquid- If SCl2 is the reagent and is used by itself the process is regulated to proceed as in Equation .9. In that case, upon the plates adjacent to point I4 the reaction will proceed mostly as in Equation 4. Some of the SCl2 will, however, spill over unrcactcd and ow downward with the S2012 formed by the reaction. This S2Cl2 will react with more CS2 as in Equation 2. As the liquids descend from plate to plate a point will be reached at which Reaction 2 will begin to predominate. Molten sulphur, or sulphur in solution will also begin to be an important constituent of the liquids and the proportion of sulphur will become greater and greater as the liquid descends. On the lowermost plate the pool of liquid will consist largely of molten sulphur, with only a small amount of residual S2Cl2. This pool is scrubbed with CS2, which ls in great excess over the S2012 reaching that point and the S2012 largely eliminated as in Equation 6.

If S2C12 is also present the process is preferably regulated to proceed in accordance with Equation l0. In that case any residual SCl2 linding its way to the lowermost plate will be scrubbed out of a pool consisting of sulphur in solution in SeCla.

The elemental sulphur liberated by the reaction, in molten condition or in solution in S2Cl2, finds its way into receiver I6. Thence lt is drawn cil' through pipe I8. If the sulphur is molten, a

part of it may be used to replenish the CS2. The balance is transferred'to the chlorinator, about to be described, and chlorinated to replenish the SCl2 used in the same period of time. If the sulphur is in solution in S2Cl2, a portion of this so- I lution is diverted to still I9 by opening valve 20. The quantity allowed to enter still I9 from time to time should be suficient to contain a quantity of sulphur equivalent to that entering the system as CS2 in the same time. Still I9 is provided with steam jacket 2|, by means of which the S2Cl2 is distilled off from the sulphur. The latter is discharged through valve 22 and used to replenish the CS2 or otherwise as desired. The vaporized S2C12 is transferred through pipe 23 and valve 24 to chlorinator 25, where it is condensed by cold water flowing through jacket 26. The balance of the solution of sulphur in S2Cl2 is passed directly to chlorinator 25 through pipe 21 and valve 28. Chlorine is then admitted through pipe 29 and valve 30 and the mixture of S2Cl2 and elemental sulphur chlorinated just suiciently to replenish the original mixture of SCl2 and S2Cl2 used in the same period of time. When the chlorination is finished, the charge is blown over into storage 2, by means of compressed air admitted through pipe 3I and valve 32. During this operation valve 31 may be opened, allowing storage 2 to be vented through pipe 38.

The CCL; produced by the reaction, being more volatile than the S2Cl2 or elemental sulphur, bubbles upward with the CS2 through the pools of liquid on the plates. Above point I4 the CC14 continues upward, carrying a small quantity of SCl2 and S2Cl2. The latter is fractionated out on the plates between point I4 and point 39, at which point the liquid product is drawn oi through pipe to storage not shown.

Above point 39 the residual SCl2, if any, continues to rise, the CCl4 being fractionated out of it, until it nally leaves the column at point 4I, still in vapor phase. This SCl2 is then liqueiied in condenser 42 and returned to the column at point 43.

If elemental chlorine is the chlorinating agent employed, still I9 and chlorinator 25 become superfluous. In that case only molten sulphur will he drawn off from. receiver I6 and the quantity will necessarily be just sufficient to replenish the CS2.

At the point of introduction of the CS2 into the column there is of course a slight back pressune caused by the resistance of the aggregate head of liquids on the plates; butin practice this does not exceed 2 pounds per square inch and is generally less.

The temperature at various points in the column depends upon whether the. chlorine is in'- troduced as elemental chlorine, as SCl2 or S2Cl2; also upon the rate of admission of the reagents and the temperature maintained in the base of the column by the' steam jacket. In practice, the conditions are regulated so that the CS2 is immediately vaporized and the sulphur is in a molten state, but the S2Cl2 is maintained in liquid phase.

Example In an apparatus of the type illustrated and described, including a 58 plate column 4 inches in diameter and 29 feet high, '76 pounds of CS2 were introduced at point 9. A mixture consisting of 134 pounds of SCl2 and 261 pounds of S2Cl2 were introduced in the same period of time at point I4. pounds of sulphur and 163 pounds of S2Cl2 were drawn off from receiver I6 and 158 pounds CCL; product drawn oiT at point 39. The latter contained 4 pounds or 2.56 per cent of SCl2 but no CS2 or S2012. The product was purified by treatment with lime and yielded 154 pounds of high grade carbon tetrachloride.

It will be noted that in this example the yield of carbon tetrachloride was substantially quantitative with respect to both the sulphur chloride and the carbon disulphide. It will also be noted that the elemental sulphur drawn off was more than suicient to replace that introduced as CS2 and that the S2Cl2 drawn oi was more than equivalent to that derived from the SCl2 by the reaction.

- My process as above described is of course essentially a continuous process and on that account advantageous as compared with the batch processes heretofore used. It has, moreover, the further advantage that it avoids the hazards incident to operations carried out with large bodies of carbon disulphide.

`In the drawing I have illustrated the column as of the bubble cap plate type; but, although I prefer that type of reactor, it is to be understood that I do not wish to be limited thereto, as a packed column or other equivalent reactor might possibly be made to serve the purpose.

Although I have described the foregoing process as carried out by means of elemental chlorine or sulphur dichloride or monochloride, I do not wish to be limited to those reagents, as other chlorinating agents, such as sulphuryl chloride, antimony pentachloride, etc., are theoretically suitable chlorinating agents.

I have described my invention as illustrated by the reaction of chlorine with carbon disulphide. However, I do not wish to be limited to this re.- action as my invention is generally applicable to reactions which in a batch operation tend to reach an equilibrium and stop and which reverse when an effort is made to recover the products. In general, my invention is applicable to reactions in which one of the reagents and an end product or intermediate product boils at a relatively high temperature, compared with the other reagent or product, if any, or both; or, in short,

to any reaction in which, by temperature control, one reagent can be caused to pass in vapor phase in contact with successive pools oi' the other reagent or one of its intermediates or end products moving in liquid phase in the opposite direction.

I claim as my invention:

1. The process for production of carbon tetralchloride which comprises causing a large excess phide to rise through a lower reaction zone oi' a column reactor to a higher reaction zone of said column, in vapor phase; there chlorinating the carbon and sulphur substantially completely out of it, producing carbon tetrachloride and sulphur monochloride; causing the sulphur monochloride to descend in said lower reaction zone in liquid phase, counterilow with respect to more carbon disulphide rising therein in vapor phase, producing more carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said lower reaction zone: causing the carbon tetrachloride to rise in said lower reaction zone and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, in vapor phase; and withdrawing .free sulphur from below said lower reaction zone and carbon tetrachloride from above said higher reaction zone.

3. 'I'he process for production of carbon tetrachloride which comprises causing carbon disulphide to rise through a lower reaction zone of a column reactor to a higher reaction zone of said column, in vapor phase; there subjecting it to elemental chlorine', producing carbon tetrachloride and sulphur monochloride; causing -the sulphur monochloride to descend in said lower reaction zone, in liquid phase, counterflow with respect to more carbon disulphide rising therein in vapor phase, producing more carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said lower reaction zone; causing the carbon tetrachloride to rise in said lower reaction zone and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, in vapor phase; and withdrawing free sulphur from below said lower reaction zone and carbon tetrachloride from above said higher reaction zone.

4. The process for production of carbon tetra.-

chloride which comprises causing carbon disulphide to rise through a lower reaction zone oi' a column I`reactor to a higher reaction zone of said column, in vapor phase; there subjecting it to sulphur dichloride, producing carbon tetrachloride and sulphur monochloride; causing the sulphur monochloride to descend in said lower reaction zone, in liquid phase, counterilow with respect to more carbon disulphide rising therein in. vapor phase, producing more carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said lower reaction zone: causing the carbon tetrachloride to rise in said lower reaction zone and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, in vapor phase: and withdrawing free sulphur from below said lower reaction zone and carbon tetrachloride i'rom above said higher reaction zone.

5. The processior production of carbon tetrachloride which comprises causing carbon disulphide to rise through a lower reaction zone of a column reactor to a higher reaction zone of said column, in vapor phase; there subjecting it to a mixture oi' sulphur dichloride and sulphur monochloride, producing carbon tetrachloride and sulphur monochloride and liberating sulphur; causing the free sulphur and sulphur monochloride to descend in said lower reaction zone, in liquid phase, counterilow with respect to more carbon disulphide rising therein in vapor phase, produc- -ing more carbon tetrachloride and liberating more sulphur: causing the free sulphur to descend in saidlower reaction zone; causing the carbon tetrachloride to rise in said lower reaction zone and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, in vapor phase; and withdrawing free sulphur from below said lower reaction zone and carbon tetrachloride from above said higher reaction zone.

6. The process for production of carbon tetrachloride which comprises causing carbon disulphide to rise through a lower reaction zone of a column reactor :to a higher reaction zone of said column, in vapor phase; -there subjecting it to an excess o! sulphur dichloride, producing carbon .tetrachloride and sulphur monochloride; causing thesulphur monochloride to descend in said lower reaction zone, in liquid phase, counterilow with respect to more carbon disulphide rising therein in vapor phase, producing more carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said lower reaction zone; causing the carbon tetrachloride to rise in said lower reaction z one and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, to a rectifying zone, in vapor phase; and withdrawing free sulphur and excess sulphur monochloride from below said lower reaction zone and carbon tetrachlorideand excess sulphur dichlo- .ride from dierent portions of said rectifying part of the withdrawn sulphur to replace sulphur V e monochloride used up in the reaction.

8. The process for production of carbon tetrachloride which comprises causing carbon disulphide to rise through a lower reaction zone of a column reactor to a higher reaction zone of said column, in vapor phase; there subjecting it to sulphur dichloride, producing carbon tetrachloride and sulphur monochloride;- causing the sulphur monochloride to descend in said lower reaction zone in liquid phase, counterflow with respect to more carbon disulphide rising therein in vapor phase, producing more carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said lower reaction zone; causing the carbon tetrachloride to rise in` said lower reaction zone and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, in vapor phase; withdrawing free sulphur from below said lower reaction zone and carbon tetrachloride from above said higher reaction zone; and treating a part of the withdrawn sulphur to restore sulphur dichloride used up in the reaction.

9. The process for production of carbon tetrachloride which comprises causing a large excess of sulphur monochloride to descend in a reaction zone of a column reactor, in liquid phase, counterow with respect to carbon disulphide rising therein'in vapor phase, producing carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said reaction zone; causing the carbon tetrachloride to rise in said reaction zone, in vapor phase; withdrawing free sulphur and excess sulphur monochloride from below and carbon tetrachloride from above said reaction zone; and treating a part of the withto sulphur dichloride, producing carbon tetra-v chloride and sulphur monochloride; causing the sulphur monochloride to descend in said lower reaction zone, in liquid phase, counterflow with respect to more carbon disulphide rising therein in vapor phase, producing more carbon tetrachloride and liberating sulphur; causing the free sulphur to descend in said lower reaction zone: causing the carbon tetrachloride to rise in said lower reaction zone and, together with the carbon tetrachloride produced in said higher reaction zone, to rise in said higher reaction zone, in vapor phase; withdrawing free sulphur from below said lower reaction zone and carbon tetrachloride from above said higher reaction zone; and treating a part of the withdrawn sulphur to replace the sulphur dichloride and another part of the withdrawn sulphur to replace the carbon disulphide used up in the reaction.

JOY E. BEANBLOSSOM. 

